1. Field of the Invention
This invention relates in general to electrophotographic reproduction, and in particular to electrophotographic reproduction utilizing hydrazone materials of the composition; ##STR2## as the active material in the p-type charge transport layer of a multi-layer photoconductor system.
2. Description of the Prior Art
Electrophotographic processes and materials, such as xerography, are of course well known. Fundamentally, such processes involve the formation of a uniform electrostatic charge upon a normally insulating plate or element under "dark" conditions. Thereafter, the element is exposed to light in an imagewise manner to render the light struck portions of the element conductive thereby permitting the electrostatic charge to be conducted from the surface of the element. Thus a latent image in the form of charged surface areas are formed on the portions of the surface not struck by light. The latent electrostatic image on the surface of the element is then typically developed by exposure to an oppositely charged powder, i.e., a toner which is held to the charged portion of the element by the affinity of the toner for the opposite charge. The discharged portion of the element displays no such affinity for the toner. The thus formed image of toner is thereafter transferred to another surface, such as paper, and adhered thereto by, for instance, pressure sensitive, heat sensitive, etc, adhesives admixed with the toner.
A particularly useful electrophotographic element is that in which a charge generation layer, which is responsive to actinic radiation to generate electron-hole pairs, is utilized in conjunction with a p-type charge transport layer adjacent thereto. Numerous charge generation layers responsive to selected actinic radiation are known. The charge transport layer is not responsive to actinic radiation under the operating conditions, but serves to transport the positive charge from the charge generation layer, to, depending upon the particular system involved, the surface of the negatively charged transport layer at which the image is formed, or alternatively, to a conductor in a positively charged system. U.S. Pat. No. 3,837,851 discusses an electrophotographic plate utilizing as the active material in the charge transport layer a tri-aryl pyrazoline compound.
Hydrazones of a differing nature than those with which the instant invention is concerned have been employed in photoconductors essentially as a material responsive to actinic radiation. U.S. Pat. No. 3,717,462, issued Feb. 20, 1973, discloses such use of a hydrazone compound. Other similar uses of hydrazone compounds, in general are to be found in U.S. Pat. No. 3,765,884.
In summary, the prior art has recognized the use of charge transport layers in conjunction with distinct charge generating layers, but has not suggested the use of hydrazones in general, and particularly the hydrazones of the instant invention, for use as the active material in a charge transport layer. On the other hand, hydrazones differing from the specific hydrazones of the instant invention have been employed as light responsive materials as opposed to charge transport materials.